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http://nopr.niscpr.res.in/handle/123456789/15369| Title: | Conformational features of a hexapeptide model Ac-TGAAKA-NH2 corresponding to a hydrated α helical segment from Glyceraldehyde 3-phosphate dehydrogenase role of turns in helix folding |
| Authors: | Sasidhar, Y U Ramakrishna, V |
| Issue Date: | Feb-2000 |
| Publisher: | NISCAIR-CSIR, India |
| Abstract: | Recent analysis of α helices in protein crystal structures, available in literature, revealed hydrated α helical segments in which, water molecule breaks open helix 5 →1 I hydrogen bond by inserting itself, hydrogen bonds to both C=O and NH groups of helix hydrogen bond without disrupting the helix hydrogen bond, and hydrogen bonds to either C=O or NH of helix hydrogen bond. These hydrated segments display a variety of turn conformations and are thought to be 'folding intermediates' trapped during folding-unfolding of α helices. A role for reverse turns is implicated in the folding of α helices. We considered a hexapeptide model Ac-1TGAAKA6-NH2. from glyceraldehyde 3-phosphate dehydrogenase ,corresponding to a hydrated helical segment to assess its role in helix folding. The sequence is a site for two 'folding intermediates'. The conformational features of the model peptide have been investigated by 1H 2D NMR techniques and quantum mechanical perturbative configuration interaction over localized orbitals (PCILO) method. Theoretical modeling largely correlates with experimental observations. Based upon the amide proton temperature coefficients, the observed dαn(i, i+ 1), dαn(i, i+2), dnn(i, i+ 1 ), dβn(i, i+ 1) NOEs and the results from theoretical modeling, we conclude that the residues of the peptide sample α helical and neck regions of the Ramachandran φ,Ψ map with reduced conformational entropy and there is a potential for turn conformations at N and C terminal ends of the peptide. The role of reduced conformational entropy and turn potential in helix formation have been discussed. We conclude that the peptide sequence can serve as a 'folding intermediate' in the helix folding of glyceraldehyde 3-phosphate dehydrogenase. |
| Page(s): | 34-44 |
| ISSN: | 0975-0959 (Online); 0301-1208 (Print) |
| Appears in Collections: | IJBB Vol.37(1) [February 2000] |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| IJBB 37(1) 34-44.pdf | 1.11 MB | Adobe PDF | View/Open |
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